There are many instances where check valve assemblies are employed in an in-line application, for precluding reverse flow of pressurized fluids moving through the conduit within which the check valve is installed. Typically, such installations are employed where a fluid—typically a liquid, but possibly a gas—is pumped from one location to a suitable receiving vessel such as a tank or other storage vessel.
When the fluid is being delivered, it is pressurized; and when delivery stops, pressurization of the fluid is also removed. However, typically it is undesirable, or in some cases forbidden, for there to be back flow of the fluid from the receiving vessel towards the source from whence it came. For that purpose, a check valve is typically installed in line within the conduit to which the pressurized fluid is delivered to the receiving vessel.
Moreover, in many such circumstances, the pressurized fluid is one which is dangerous to handle, or which may have corrosive or other deteriorating effects on ordinary check valve assemblies, particularly such assemblies that are typically used and which employ spring members to assure that they close when unpressurized. Examples of such fluids include, for purposes of illustration only, various acids such as hydrochloric, sulphuric, or nitric acid, gases such as ammonia or chlorine gas, and so on.
Typically, especially in industrial applications and the like, a positive gauge pressure occurs across a check valve, when the fluid on the inlet side thereof is pressurized, such that a gauge pressure between the inlet and outlet side may range only from a few psi up to, say, 20 psi. Moreover, after delivery of the pressurized fluid gases, the gauge pressure across a check valve may reduce to approximately zero or even become a negative value—that is, the pressure at the outlet side of the check valve may be higher than the pressure at the inlet side of the check valve.
It is known in many industrial applications to replace check valves annually, or sometimes many times during the year. That procedure is costly for a number of reasons: It requires the use of skilled personnel having plumbing and/or pipe fitting training, it may require visits to the field where the installation of the check valve is placed, and in any event it is costly because it requires maintenance of inventory and replacement of that inventory as check valves are withdrawn therefrom.
A principal object of the present invention is to provide check valve assemblies which effectively employ no moving parts, because of its employment of an elastomeric valve member which will change its shape and dimension. Moreover, check valve assemblies in keeping with the present invention are typically manufactured from materials which are impervious or at least resistant to corrosion or deterioration in the presence of the pressurized fluid with which they are to work.